LDHA and head and neck squamous cell carcinoma: Aldehyde dehydrogenase (ALDH) is a selective marker of CSCs in breast cancer, bladder cancer, embryonic rhabdomyosarcoma, head-and-neck squamous cell carcinoma, and lung cancer, and its high expression of ALDH causes resistance to a variety of chemotherapy and targeted agents, such as cisplatin, etoposide, fluorouracil, and gefitinib (Ginestier et al., 2007; Huang et al., 2013).